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.\"
.\" Copyright 2002 Massachusetts Institute of Technology
.\"
.\" Permission to use, copy, modify, and distribute this software and
.\" its documentation for any purpose and without fee is hereby
.\" granted, provided that both the above copyright notice and this
.\" permission notice appear in all copies, that both the above
.\" copyright notice and this permission notice appear in all
.\" supporting documentation, and that the name of M.I.T. not be used
.\" in advertising or publicity pertaining to distribution of the
.\" software without specific, written prior permission. M.I.T. makes
.\" no representations about the suitability of this software for any
.\" purpose. It is provided "as is" without express or implied
.\" warranty.
.\"
.\" THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''. M.I.T. DISCLAIMS
.\" ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
.\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
.\" SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
.\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
.\" USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
.\" ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
.\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd August 16, 2013
.Dt PSELECT 2
.Os
.Sh NAME
.Nm pselect
.Nd synchronous I/O multiplexing a la POSIX.1g
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/select.h
.Ft int
.Fo pselect
.Fa "int nfds"
.Fa "fd_set * restrict readfds"
.Fa "fd_set * restrict writefds"
.Fa "fd_set * restrict exceptfds"
.Fa "const struct timespec * restrict timeout"
.Fa "const sigset_t * restrict newsigmask"
.Fc
.Sh DESCRIPTION
The
.Fn pselect
function was introduced by
.St -p1003.1g-2000
as a slightly stronger version of
.Xr select 2 .
The
.Fa nfds , readfds , writefds ,
and
.Fa exceptfds
arguments are all identical to the analogous arguments of
.Fn select .
The
.Fa timeout
argument in
.Fn pselect
points to a
.Vt "const struct timespec"
rather than the (modifiable)
.Vt "struct timeval"
used by
.Fn select ;
as in
.Fn select ,
a null pointer may be passed to indicate that
.Fn pselect
should wait indefinitely.
Finally,
.Fa newsigmask
specifies a signal mask which is set while waiting for input.
When
.Fn pselect
returns, the original signal mask is restored.
.Pp
See
.Xr select 2
for a more detailed discussion of the semantics of this interface, and
for macros used to manipulate the
.Vt "fd_set"
data type.
.Sh RETURN VALUES
The
.Fn pselect
function returns the same values and under the same conditions as
.Fn select .
.Sh ERRORS
The
.Fn pselect
function may fail for any of the reasons documented for
.Xr select 2
and (if a signal mask is provided)
.Xr sigprocmask 2 .
.Sh SEE ALSO
.Xr kqueue 2 ,
.Xr poll 2 ,
.Xr select 2 ,
.Xr sigprocmask 2 ,
.Xr sigsuspend 2
.Sh STANDARDS
The
.Fn pselect
function conforms to
.St -p1003.1-2001 .
.Sh HISTORY
The
.Fn pselect
function first appeared in
.Fx 5.0 .
.Sh AUTHORS
The first implementation of
.Fn pselect
function and this manual page were written by
.An Garrett Wollman Aq wollman@FreeBSD.org .
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